Electrolytes and Body Fluids — MCQs

Electrolytes and Body Fluids Indian Medical PG Practice Questions and MCQs

Question 151: Calcium absorption is affected by-

A. Calcitriol
B. PTH
C. Proteins
D. All of the options (Correct Answer)

Explanation: ***All of the options*** - **Calcitriol**, **parathyroid hormone (PTH)**, and **proteins** all play crucial roles in regulating calcium absorption and metabolism. - While calcitriol directly enhances intestinal calcium absorption, PTH indirectly influences it via calcitriol synthesis, and proteins are necessary for calcium transport and binding. *Calcitriol* - **Calcitriol** (1,25-dihydroxyvitamin D3) is the hormonally active form of vitamin D, which is essential for stimulating calcium absorption in the intestine. - It increases the synthesis of **calcium-binding proteins (calbindins)** in enterocytes, facilitating calcium uptake. *PTH* - **Parathyroid hormone (PTH)** primarily regulates calcium levels by stimulating its release from bone and increasing reabsorption in the kidneys. - It also indirectly enhances intestinal calcium absorption by stimulating the **renal conversion of 25-hydroxyvitamin D to calcitriol**. *Proteins* - Various **proteins** are involved in calcium transport and absorption, including calcium-binding proteins (e.g., calbindin) in the gut. - Dietary protein intake can also influence calcium balance; however, specific mechanisms regarding direct absorption are more complex and indirect compared to calcitriol.

Question 152: What is the percentage of water in adult human being?

A. 40%
B. 50%
C. 70%
D. 60% (Correct Answer)

Explanation: ***60%*** - The human body is composed of approximately **60% water** by weight in adult males. - This percentage can vary slightly based on age, sex, and body composition, but 60% is a widely accepted average. *40%* - 40% is generally considered too low for the average total body water content in an adult human. - While certain tissues have lower water content, the overall average is significantly higher. *50%* - 50% is below the typical average for most adult humans, although it might be seen in individuals with a higher percentage of **adipose tissue**, as fat contains less water than lean tissue. - This figure is more common in older adults or individuals with a higher body fat percentage. *70%* - 70% is generally considered on the higher side for the average adult human, more characteristic of infants and young children whose bodies have a higher water content. - While some lean individuals may approach this percentage, it is not the typical average for adults.

Question 153: Major portion of body water lies in:

A. Extracellular
B. Interstitial fluid
C. Intracellular (Correct Answer)
D. Plasma

Explanation: ***Intracellular*** - Approximately **two-thirds (60%)** of the total body water is located **inside cells** (intracellular fluid, ICF). - In a 70 kg adult male, out of ~42L total body water, approximately **28L is intracellular**. - This fluid is crucial for maintaining **cell volume**, metabolic processes, and overall cell function. - The ICF contains high concentrations of potassium, magnesium, and phosphate. *Extracellular* - The **extracellular fluid (ECF)** compartment accounts for about **one-third (40%)** of the total body water (~14L in a 70 kg adult). - While vital for nutrient and waste transport, it is a smaller volume compared to the intracellular compartment. - ECF is further divided into interstitial fluid (~75% of ECF) and plasma (~25% of ECF). *Interstitial fluid* - Interstitial fluid is a **component of extracellular fluid**, not a major body water compartment on its own. - It accounts for only about **10-11L** in a typical adult, which is less than the intracellular volume. - It surrounds tissue cells and facilitates exchange between plasma and cells. *Plasma* - Plasma is the **smallest fluid compartment**, representing only about **3-3.5L** (~8% of total body water). - While essential for circulation and transport, it contains far less water than the intracellular compartment. - Plasma is the liquid component of blood, excluding cellular elements.

Question 154: Which of the following is true about body fluid osmolarity?

A. Major contributor is Na+ (Correct Answer)
B. Measured by dilution method
C. Major contributor is proteins
D. ECF osmolarity is 250 mOsm/L

Explanation: ***Major contributor is Na+*** - **Sodium (Na+)** and its associated anions (chloride and bicarbonate) are the primary determinants of **extracellular fluid (ECF) osmolarity** due to their high concentration and inability to freely cross cell membranes. - The concentration of effective solutes like Na+ dictates the **osmotic movement of water** between fluid compartments. *Measured by dilution method* - **Dilution methods** are typically used to measure **body fluid volumes**, such as total body water or ECF volume, by tracking the distribution of a known tracer. - **Osmolarity** is measured by an **osmometer**, which determines the number of solute particles per unit of solvent, often based on freezing point depression. *Major contributor is proteins* - While proteins are present in body fluids, their contribution to **total osmolarity** is relatively small compared to electrolytes, especially in the **extracellular fluid**. - Proteins exert an **oncotic pressure**, which is important for fluid distribution between plasma and interstitial fluid, but not the primary determinant of overall osmolarity. *ECF osmolarity is 250 mOsm/L* - The normal range for **ECF osmolarity** in humans is approximately **280-295 mOsm/L**, with an average of around 285-290 mOsm/L. - A value of 250 mOsm/L would indicate **hypoosmolality**, which is a deviation from the normal physiological range.

Question 155: Normal amount of sodium in plasma is (in mEq/L)

A. 95
B. 143 (Correct Answer)
C. 120
D. 175

Explanation: ***Correct: 143 mEq/L*** - The normal physiological range for **sodium concentration in plasma** is typically between **135 and 145 mEq/L**. - Therefore, **143 mEq/L** falls right within the healthy range and represents a normal value. *Incorrect: 95 mEq/L* - A plasma sodium concentration of **95 mEq/L** would indicate severe **hyponatremia**. - This level is significantly below the normal range and would be associated with severe neurological symptoms such as **seizures or coma**. *Incorrect: 120 mEq/L* - A plasma sodium concentration of **120 mEq/L** would indicate **hyponatremia**. - While not as severe as 95 mEq/L, it is still below the normal range and could lead to symptoms like **nausea, malaise, and headache**. *Incorrect: 175 mEq/L* - A plasma sodium concentration of **175 mEq/L** would indicate severe **hypernatremia**. - This is significantly above the normal range and could cause symptoms such as **thirst, lethargy, seizures, or even brain damage**.

Question 156: Factors that decrease insensible water losses are all, except –

A. Sedation
B. Humidified air
C. Prematurity (Correct Answer)
D. Hypothermia

Explanation: ***Prematurity*** - **Premature infants** have **thinner skin** and a larger surface area to body weight ratio, leading to **increased insensible water losses** compared to full-term infants. - Their immature skin barrier function allows for greater evaporative water loss. *Sedation* - **Sedation** can **decrease metabolic rate** and activity, leading to a reduction in insensible water losses. - It reduces ventilation rate and skin blood flow, both contributing to decreased water evaporation. *Humidified air* - Using **humidified air**, particularly with mechanical ventilation, **decreases the gradient for water evaporation** from the respiratory tract. - This directly reduces pulmonary insensible water loss. *Hypothermia* - **Hypothermia** (low body temperature) **reduces metabolic rate** and peripheral blood flow. - A decreased metabolic rate leads to lower heat production and, consequently, reduced evaporative water loss from the skin and respiratory tract.

Question 157: Two solutions with equal osmotic pressures are called:

A. Normal solution
B. Hypertonic solution
C. Isotonic solution (Correct Answer)
D. Hypotonic solution

Explanation: ***Isotonic solution*** - **Isotonic solutions** have the same solute concentration, and therefore the same **osmotic pressure**, as another solution. - In biological systems, an isotonic solution has the same osmotic pressure as the **cytosol** inside cells, preventing net water movement. *Normal solution* - "Normal solution" is a general term often referring to a solution at standard conditions or a commonly used concentration, but it does not specifically mean equal osmotic pressure. - While **normal saline** (0.9% NaCl) is isotonic to human plasma, the term "normal solution" itself is not a direct definition of equal osmotic pressure. *Hypertonic solution* - A **hypertonic solution** has a higher solute concentration and thus a higher **osmotic pressure** compared to another solution. - When a cell is placed in a hypertonic solution, water moves out of the cell, causing it to **crenate** or shrink. *Hypotonic solution* - A **hypotonic solution** has a lower solute concentration and thus a lower **osmotic pressure** compared to another solution. - When a cell is placed in a hypotonic solution, water moves into the cell, causing it to **swell** and potentially lyse.

Question 158: Which of the following methods is NOT used for measurement of body fluid volumes? (March 2013)

A. Evans blue for plasma volume
B. Inulin for extracellular fluid
C. Antipyrine for total body water
D. Creatinine clearance for blood volume (Correct Answer)

Explanation: ***Creatinine clearance for blood volume*** - **Creatinine clearance** is a measure of **glomerular filtration rate (GFR)** and kidney function. - It is **not used** to measure blood volume; rather, blood volume is typically measured using indicator dilution methods. *Evans blue for plasma volume* - **Evans blue** is a dye that binds to **plasma albumin** and remains within the intravascular space. - Its concentration can be used in the **indicator dilution method** to accurately determine plasma volume. *Inulin for extracellular fluid* - **Inulin** is freely filtered by the glomeruli but **neither reabsorbed nor secreted** by the renal tubules. - It is used to measure **extracellular fluid volume** because it distributes throughout this compartment but does not enter cells. *Antipyrine for total body water* - **Antipyrine** is a lipid-soluble substance that diffuses readily across cell membranes and distributes uniformly throughout **total body water**. - Its concentration is used in the **indicator dilution method** to determine the total water content of the body.

Question 159: Which of the following is NOT true about osmotic adaptation?

A. Due to osmolytes
B. Occurs in brain cells
C. Due to urea and glucose mainly (Correct Answer)
D. Protects against large water shift

Explanation: ***Due to urea and glucose mainly*** - Osmotic adaptation primarily involves organic osmolytes like **myoinositol**, **taurine**, **sorbitol**, and **glutamate**, not primarily urea and glucose. - While urea and glucose contribute to osmotic pressure, they are not the main adaptive osmolytes used by cells for long-term osmotic balance. - This statement is **NOT true** about osmotic adaptation. *Due to osmolytes* - Osmotic adaptation depends on the cell's ability to regulate intracellular concentration of specific **organic osmolytes** (e.g., polyols, amino acids, methylamines). - These osmolytes help fine-tune intracellular osmotic pressure without disrupting **protein function**. *Occurs in brain cells* - Brain cells are particularly vulnerable to changes in osmolality due to the skull's rigid confines, making **osmotic adaptation** critical for maintaining brain volume. - They actively regulate intracellular osmolytes to protect against **swelling or shrinking** in response to plasma osmolality changes. *Protects against large water shift* - By adjusting internal osmolyte concentrations, cells counteract osmotic gradients, thereby preventing **excessive water influx or efflux**. - This mechanism is crucial for maintaining **cell volume and function** in environments with fluctuating external osmolality.

Question 160: Which of the following is considered the active form of calcium?

A. Albumin bound calcium
B. Ionised calcium (Correct Answer)
C. Phosphate bound calcium
D. Protein bound calcium

Explanation: ***Ionised calcium*** - **Ionized calcium** (approximately 50% of total serum calcium) is the physiologically active form of calcium, responsible for most calcium-dependent bodily functions. - It directly participates in processes like **muscle contraction**, **nerve impulse transmission**, **blood coagulation**, and serves as a **second messenger** in cellular signaling. - This is the **free, unbound form** that exerts biological effects. *Albumin bound calcium* - **Albumin-bound calcium** (approximately 40% of total serum calcium) is a storage and transport form of calcium, but it is not metabolically active. - Albumin is the **primary protein** that binds calcium in the blood. - Its concentration can be affected by **albumin levels**, making corrected calcium calculations necessary in hypoalbuminemia. *Phosphate bound calcium* - **Phosphate-bound calcium** represents calcium that is complexed with phosphate and other anions (approximately 10% of total serum calcium). - Often found as insoluble salts in bone or as soluble complexes in body fluids. - While essential for bone mineralisation, this form is **not directly active** in signaling or metabolic processes. *Protein bound calcium* - **Protein-bound calcium** refers to calcium attached to various proteins, primarily **albumin** (80% of protein-bound fraction), and other proteins like globulins. - This is a **broader category** that encompasses albumin-bound calcium. - This fraction serves as a **reservoir** but is not the free, unbound calcium that performs cellular functions.

Practice by Chapter

Body Fluid Compartments and Composition

Practice Questions

Osmolality and Tonicity

Practice Questions

Sodium and Water Balance

Practice Questions

Potassium Homeostasis

Practice Questions

Calcium and Phosphate Regulation

Practice Questions

Magnesium Metabolism

Practice Questions

Fluid Shifts Between Compartments

Practice Questions

Edema Formation Mechanisms

Practice Questions

Dehydration Physiology

Practice Questions

Disorders of Electrolyte Balance

Practice Questions

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